Okay so I ruled out what it isn't. So it is what again?
A type of healing where the technique is channeling universal energy. The practitioner is someone who has been attuned to the energy and is able to act as a vessel to transmit the energy after invoking reiki ( rei -ki which loosely means spirit energy).
Make sense so far?
ANYONE has access to working with reiki. The only step one needs is the attunement process ( which cleans you out , aligns and balances you and makes you a nice clear receptacle for reiki). That is because people have become so removed from the source ( universe, god whatever you want to call it) and are a rather internally muckered lot.
It's really that simple really.
So how does it work?
I can give you my experiences and of course you can read up on it too ( hint here go look in the links section and look up the Reiki tab).
In general the practitioner is like a hollow pitcher. The practitioner invokes reiki for whatever reason ( healing, blessing, focusing, for self or one who requests it). The reiki fills the practitioner up ( think crystal clean water in a pitcher). All the practitioner does is "pour" the reiki where it is needed ( by the way the reiki is also the lead to where the "spout" is to pour as well as how long to "tip" into a person).
The difference between Reiki and using your own energy to work with is that while reiki is being used to work on another person it fills the practitioner up and at the same time works on the practioner. It's neat really.
( I lurve mah reiki)
When you use your own energy you deplete your own reserves ( unless you are drawing from another source and in that case it usually is being drawn and immediately redirected to a focal point).
Am I making sense so far?
I do hope so.
Reiki can be used to help heal and harmonize on all levels ( physical, emotional, mental, spiritual, etc).
It can be used directly ( I lay my hands on your shoulder cause it hurts) or it can be used long distance.
Reiki is not the same experience for everyone. Some people feel nothing. Others feel a huge impact and others something subtle. In my experience reiki benefits ( from a session) are not apparent immediately. So if you have a headache I suggest taking a tylenol along with your reiki .
Reiki works with your meds too by the way ( no contraindictions
).
Anyways reiki is not a bandaid method conjured up for the specifics of healoing. It is in essence (for the sincere and ....."hardcore" <---not the word I was looking for but you get the idea) it is a way of life with meditations, self reflections and more basing off of respect and universal love for all. It is a very beautiful thing if you allow it to be.
All in all reiki is a wonderful and versatile relationship with energy.
If you have any more questions feel free to ask. I hope this was helpful as an introductory summary of what reiki is.
C.S.
What IS reiki anyways? 
Linear Mode
